Der elektronische Handel - Potentiale für Unternehmen

Die digitale Infrastruktur des Internets wird in zunehmenden Maße als Marktplatz genutzt. Auch hier treffen Angebot und Nachfrage zusammen. Der grundlegende Unterschied zu traditionellen Märkten liegt in der elektronischen Abbildung von Teilen der Transaktion oder der gesamten Transaktion. Diese zunehmende Unterstützung bzw. Automatisierung aller Ebenen und Phasen des kommerziellen Handels führt zu elektronischen Marktplätzen, elektronischem Zahlungsverkehr sowie elektronischen Lieferungen von mediatisierten Gütern und Dienstleistungen. Prof. Dr. Dr. h.c. Arnold Picot, Dominik K. Heger und Dr. Rahild Neuburger Universität München, analysieren in diesem Beitrag die Einsatzmöglichkeiten das elektronischen Handels und die damit verbundenen Herausforderungen an die Unternehmen.Elektronischer Markt; Unternehmen

Accessibility appraisal of integrated land-use-transport strategies: methodology and case study for the Netherlands Randstad area

Conventional approaches to measuring accessibility benefits are not capable of fully measuring the total accessibility benefits of integrated land-use-transport strategies, in which both land-use and transport changes form part of the policy strategy. In this paper a comprehensive methodology for analysing accessibility impacts and accessibility benefits, which is based on location-based and utility-based accessibility measures within an integrated land-use-transport interaction modelling framework, is described and applied in a case study. The case study examines the accessibility benefits and related user benefits of intensive mixed-use strategies aimed at increasing the density and diversity of activities around railway stations for the Randstad area of the Netherlands for the 1996-2030 period. A heavy concentration of activities near railway stations is shown to result in decreasing marginal returns for public-transport users and disbenefits for car users. © 2006 a Pion publication printed in Great Britain

The Amidase Domain of Lipoamidase Specifically Inactivates Lipoylated Proteins In Vivo

BACKGROUND:In the 1950s, Reed and coworkers discovered an enzyme activity in Streptococcus faecalis (Enterococcus faecalis) extracts that inactivated the Escherichia. coli and E. faecalis pyruvate dehydrogenase complexes through cleavage of the lipoamide bond. The enzyme that caused this lipoamidase activity remained unidentified until Jiang and Cronan discovered the gene encoding lipoamidase (Lpa) through the screening of an expression library. Subsequent cloning and characterization of the recombinant enzyme revealed that lipoamidase is an 80 kDa protein composed of an amidase domain containing a classic Ser-Ser-Lys catalytic triad and a carboxy-terminal domain of unknown function. Here, we show that the amidase domain can be used as an in vivo probe which specifically inactivates lipoylated enzymes. METHODOLOGY/PRINCIPAL FINDINGS:We evaluated whether Lpa could function as an inducible probe of alpha-ketoacid dehydrogenase inactivation using E. coli as a model system. Lpa expression resulted in cleavage of lipoic acid from the three lipoylated proteins expressed in E. coli, but did not result in cleavage of biotin from the sole biotinylated protein, the biotin carboxyl carrier protein. When expressed in lipoylation deficient E. coli, Lpa is not toxic, indicating that Lpa does not interfere with any other critical metabolic pathways. When truncated to the amidase domain, Lpa retained lipoamidase activity without acquiring biotinidase activity, indicating that the carboxy-terminal domain is not essential for substrate recognition or function. Substitution of any of the three catalytic triad amino acids with alanine produced inactive Lpa proteins. CONCLUSIONS/SIGNIFICANCE:The enzyme lipoamidase is active against a broad range of lipoylated proteins in vivo, but does not affect the growth of lipoylation deficient E. coli. Lpa can be truncated to 60% of its original size with only a partial loss of activity, resulting in a smaller probe that can be used to study the effects of alpha-ketoacid dehydrogenase inactivation in vivo

Mixed-valent ruthenium oxide - ruthenium cyanide inorganic film on glassy carbon electrodes as an amperometric sensor of aliphatic alcohols

A mixed-valent ruthenium oxide-ruthenium cyanide film on glassy carbon (GC/mvRuO-RuCN) electrode exhibits excellent electrocatalytic activity toward oxidation of simple aliphatic alcohols and polyhydric compounds in acidic media. Electrochemical formation of the ruthenium oxide-based chemically modified electrode can be accomplished by potential cycling or potentiostatic control in diluted sulfuric acid solutions. The attractive electrooxidation capabilities of hydroxyl-containing compounds at this modified electrode are highlighted in terms of sensitivity, stability, and catalytic action. Remarkably, the molar response of the catalytic oxidation increases on increasing the chain length of aliphatic alcohols. For example, the molar response ratio between 1-butanol and methanol is 37 in 25 mM sulfuric acid. Chromatographic separations with electrochemical detection using the GC/mvRuO-RuCN modified electrode allo rr very simple quantitation of aliphatic alcohols in real samples with linear calibration plots over about 3 orders of magnitude. The detection limits for ethanol, 1-propanol, 1-butanol, and 1-pentanol are 4, 0.8, 1, and 2 nmol injected (S/N = 3), respectively